Tractor drive



Oct. 26, 1954 C. M. O'LEARY TRACTOR DRIVE 4 Sheets-Sheet l Filed Nov. 26. 1951 CON QON

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TRACTOR DRIVE Filed Nov. 26, 195.1 4 Sheets-Sheet 3 rmel/Eff Oct. 26, 1954 c. M. OLEARY TRACTOR DRIVE Filed Nov. 26, 1951 4 Sheets-Sheet 4 /G. :9. cas/paf M. 0254/244 Patented Oct. 26, 1954 anni UITED STATES PATENT OFFICE TRACTOR DRIVE Charles M. OLeary, Los Angeles, Calif.

Application November 26, 1951, Serial No. 258,269

The present invention relates to an automatic multiple speed transmission mechanism and more particularly to an automatic multiple speed transmission mechanism in combination with a hydrokinetic torque converter which will maintain the speed ratio of the converter within a range of predetermined efficiency regardless of variations in the load.

It is an object of the present invention to provide an improved automatic multiple speed transmission.

Another object of my invention is to provide a transmission having gear ratios which are multiples of the speed and torque changes in an associated hydrokinetic torque converter which are necessary in order to keep the converter within the desired eiiiciency range.

Another object of my invention is to provide a single five speed transmission having two output shafts which may be selectively braked for steering purposes.

Another object of my invention is to provide, in combination with a hydrokinetic torque converter, an automatic multiple speed ratio transmission which will maintain the speed ratio of the converter within predetermined limits regardless of variations in the input speed of the converter.

Another object of my invention is to provide an improved mechanism for actuating a control instrumentality in response to the existence of a predetermined ratio between the speeds of two shafts.

Another object of my invention is to provide an automatic shifting mechanism for a, multiple speed transmission of the character described which consists essentially of eddy-current clutches and fluid valves.

Another object of my invention is to provide a multiple speed transmission of the character described having two output shafts which may be differentially connected.

Another object of my invention is to provide an automatic multiple speed transmission mechanism which is particularly adapted for use in trucks, tractors and military tanks.

Another object of my invention is to provide, in an automatic multiple speed transmission mechanism of the character described, an automatic shifting mechanism which is sturdy, durar able and capable of withstanding adverse conditions in the eld.

A further object of my invention is to provide a transmission which has the unusually flexible characteristics of a hydrokinetic torque converter 12 Claims. (Cl. 'I4-7195) drive, while at the same time continually operating above a predetermined high einciency.

Other objects and advantages of my invention will be apparent from the following description and claims, the novelty consisting in the features of construction, combination of parts, the unique relations of the members and the relative proportioning, disposition and operation thereof, all as is more completely outlined herein and as is particularly pointed out in the appended claims.

In the accompanying drawings, forming a part of this present specification,

Figure 1 is a plan View, partly in section, of my five-speed transmission and hydrokinetic torque converter,

Figure 2 is a plan view of my differential mechanism for determining the automatic shift points,

Figure 3 is a side elevation, showing the differential units of Figure 2,

Figure 4 is a plan View of my automatic shifting mechanism,

Figure 5 is a plan View of one of the shifting units shown in Figure 4 Which has been moved to a different position,

Figure 6 is a sectional view along the line 6-5 in Figure 4, showing my eddy current clutch,

Figure 7 is a sectional View along the line 1--1 in Figure 5, showing the specific construction of one of my fluid valves,

Figure 8 shows the representative torque and efficiency curves of the torque converters employed in the mechanism of Figure l, and

Figure 9 is a side elevation, partly in section, showing my differential unit Which may be engaged into operative relationship with my transmission shown in Figure 1.

Referring to the drawings, I will first describe my five speed transmission, which is shown in Figure 1.

Connected to the engine (not shown) is input shaft l of hydrokinetic torque converter l2. Although converter I2 may be of any suitable construction to provide an eiciency curve similar to that shown in Figure 8, I prefer to use a converter i2 which may be alternatively shifted back and forth from a fluid drive connection to a direct drive connection. Such a hydrokinetic torque converter is particularly described in my application Serial No. 263,419, filed December 26, 1951. y

Output shaft I4 of hydrokinetic torque converter I2 is provided with a brake It and is supported within a bearing cartridge i8. Integrally attached to the end of output shaft It is a pinion gear 2G which meshes with a right-hand bevel gear 22 lioatingly mounted on transmission reversing shaft 24.

Clutch teeth 28 form a clutch face on bevel gear 22, and are adapted to operatively engage the opposing clutch teeth 28 of clutch member S0 which is keyed or splined to shaft 24 in slideable engagement therewith.

Shaft 24 is journaled in bearings 32 and 34. Disposed about the opposing ends of shaft 24 are clutches 85 and 38, which respectively connect gears 40 and 42 to the shaft 24 upon engagement. Gears 40 and 42 are operatively engaged to the respective gears 44 and 43, gear 44 being integrally attached to a cylindrical shaft 48.

Shaft 48 is supported in bearings 58 and 52 which are integrally attached to the transmission housing.

An integral ring gear 54 is carried as an integral part of shaft 48 by means of flange 56 at the end of shaft 48. The outer periphery 58 of ring gear 54 is smooth so as to form a brake drum to receive brake band 80. A plurality of gears 62, which are mounted on shafts 64, mesh with the internal ring gear 54. Mounted on the other ends of shafts 84 are gears 68. Shafts 84 are journalcd in bearings 68 which are carried by a planet cage carrier 10. Thus, planet cage carrier 10 carries bearings 88, shafts 84, gears 62 and gears 68.

In operative engagement with gears 68 is a gear 12 which forms an integral part of a tubular shaft 14. Also forming an integral part of tubular shaft 14 is a brake drum 16 which may be operatively engaged by a brake band 18. Tubular shaft 14 is journaled in bearings 8|) and 82 which are affixed to the transmission housing.

Planet cage carrier 10 is keyed or splined to a central shaft 84 which is journaled in bearing 86 carried by shaft 48 and bearing 88 carried in shaft 14. The outer ends of shaft 84 are mounted in bearings 98 and 92, respectively, which are carried in the transmission housing. A pair of gears 84 and 86 are integrally attached to the respective ends of shaft 84.

Opposing clutch members 98 and |00 are carried by shafts 84 and 48, respectively, these two clutch members together forming a clutch Clutch members 98 and |80 are keyed or splined to shafts 84 and 48, respectively, so as to rotate with those shafts. Although clutch |0I may be of any conventional construction, I prefer to use a hydraulically operated clutch which may be actuated by admitting fluid under pressure thereto.

Engagement of clutch members 98 and |08 is effected by moving hydraulically operable clutch plates |02 and |84 on clutch members 98 and |00, respectively, together into a frictional contact with each other. An annular fluid pressure chamber |05 is disposed about a tubular extension |08 of clutch member |00. Fluid is conned within chamber |08 by means of packing rings ||0 in tubular extension |88. Fluid enters the clutch system through port H2 which is connected to fluid pressure chamber |06. The fluid then passes through radial passage ||4 into tubular passage ||6 which conveys the fluid to chamber ||8 within clutch member 98. Sealing rings |20 are provided on shaft 84 to confine the clutch actuating fluid to chamber ||8. Upon actuation of clutch |0|, tubular shaft 48 and central shaft 04 will be connected so as to turn as a single unit.

Gear 94 at one end of central shaft 84 drives a plurality of planet gears |22 which are carried on shafts |24. Shafts |24 are mounted in a planet carrier |26 which is integrally connected to transmission output shaft |20. A brake fiange |38 is mounted on the ends of shafts |24 so as to move as an integral unit with planet cage carrier |26. Brake band |32 is operatively engageable with brake flange |38 to selectively arrest the rotary motion of planet carrier |28.

An internal gear |34 which is carried by reaction drum |38 meshes with the planet gears |22. Annularly disposed about reaction drum |36 is a brake band |38 which may be used to stop rotation of drum |36. A gear |40 is externally mounted upon drum |36 for use in connection with my differential unit which will be hereinafter described.

Reaction drum |36 is formed in a tubular shaft |4| at one end, whereby drum |38 can be sup- :ported through shaft |4| by bearing |42 that is mounted within the transmission housing |44. Bearing |46 carried by drum |38 supports the transmission output shaft |28. Output shaft |28 is further supported by bearing |48 in housing |44.

Splined or keyed to shaft 84 near the other end thereof is a clutch member |50 similar to clutch member 98. Clutch member |52 is keyed or splined to the cylindrical shaft 14 to form, together with clutch member |50, the complete clutch |53. Clutch plates |54 and |56 are keyed lor splined to clutch members |52 and |50, respectively, and are adap-ted to be compressed together by uid pressure in the same manner as clutch plates |02 and |04.

Fluid pressure chamber |58 is annularly disposed about a tubular extension |60 of clutch member |52, uid being sealed within chamber |53 by means of packing rings |82. Fluid is con- -'veyed into chamber |58 through a fluid port |64,

and this fluid passes from chamber |58 through a fluid passage |88 and communicates through cylindrical passage |68 with fluid chamber |10 in clutch member |50.

Fluid is confined within chamber |10 by means of sealing rings |12 which are annularly disposed between shafts 84 and 14.

It will be noted that clutches |0| and |53 are identical in construction and that actuation of 'either of these clutches will create the same mechanical result by effecting the same gear ratio between reversing shaft 24 and output shaft |28. This occurs because engagement of clutch |53 locks quill shaft 14 to shaft 84. This locks planet cage 10 which is splined to shaft 84, to the quill shaft 14. Since no relative rotation can occur between cage 18 and quill shaft 14. no relative rotation can occur between quill shaft 14 and gears 52, 66 and 54, so that quill shaft 48, which is integral with gear 54, rotates in a l to 1 ratio with quill shaft 14. Thus, the same result is reached by engaging clutch |53 as i.; effected by engaging clutch |0|. Thus, a single clutch could `be utilized in place of the pair of clutches |02 and |53.

However, my automatic shifting mechanism is simplified by the use of two fluid actuated clutches instead of using a single clutch. This will become more apparent from the description of my automatic shifting machinism.

Gear 96 integrally mounted on the end of internal shaft 84, drives a plurality of planet gears |22 which are rotatably mounted on shafts |24. Shafts |24 are aiiixed in planet carrier |26 which forms an integral part of output shaft |28. Affixed to the outer ends of shafts |24 is a brake flange |30 which may be operatively engaged by a brake band |32.

An internal gear |34 is carried by reaction drum |35 and meshes with the planet gears |22. Brake band |33 is disposed about reaction drum |35. Gear Idil is carried on the outside of drum |36 to engage the differential unit which will be hereinafter described.

A tubular shaft |4| is formed at one end of reaction drum |38 and. is supported in bearing |42 which is mounted in the transmission housing |44. Bearing |45 is carried by reaction drum |36 and serves to support transmission output shaft |28. Output shaft |23 on this side of the transmission is also supported by bearing |43 which is mounted in housing |44.

My five-speed transmission may be used in either a forward or a reverse drive connection. I provide a reverse bevel gear which engages the pinion gear 20 on the side thereof opposite the engagement between pinion gear 20 and bevel gear 22. Bevel gear 'M is floatingly mounted on transmission reversing shaft 24 and is provided with clutch teeth |78 which are adapted to be selectively engaged and disengaged with the clutch teeth |18 on clutch member 30. Engagement between clutch teeth 28 and clutch teeth 28 causes forward rotation of the transmission members, while engagement between clutch teeth |15 and H3 causes reverse rotation of the transmission members.

In order to shift my transmission into its lowest gear, which is a four to one reduction, clutch 36 and brake band 'i8 are engaged. This provides a two to one reduction ratio between gears 40 and 44, and also a two to one reduction ratio between gears 54, 52, 66 and l2, this latter two to one reduction being applied to shaft 84 through planet ca-ge 70 which is keyed or splined thereto.

In order for this four to one gear reduction to be applied to output shafts |28, it is necessary for brake bands |38 to lock reaction drums |38 into stationary relationship with the transmission housing. Any further gear reduction may be applied between shaft 84 and shaft |28 by making gears 34 and 918 and planet gears |22 of the proper relative sizes. Thus, in the preferred embodiment of my invention, I provide a fixed five to one gear reduction between shaft 84 and shafts |23.

In order to shift my transmission from the four to one reduction ratio of low gear into a two to one reduction ratio in second gear, I release band T58 and engage clutch lill. Clutch mi locks shafts 48 and 84 together, whereby the only gear reduction will be between gears 40 and 134, which cause a two to one reduction.

In order to shift from second to third gear, I release clutches 38 and |6| and engage clutch 3S and band fit'. Engagement between gears 42 and i8 causes a two to one overdrive, but there is also a two to one reduction between gears l2, 86, 82, 54 and the planet cage carrier l0, which is keyed or splined to the central shaft 84. This two to one overdrive in combination with a two to one reduction will cause third gear to be a one to one ratio.

Shifting now from third gear into fourth gear, I release band S0 and engage clutch |53. Clutch |53 locks tubular shaft i4 to central shaft 84, 'whereby the only two gears which must be considered are gears i2 and 4t2, which provide a two to one overdrive.

It should be noted at this point that the two to one overdrive of fourth gear could also be effected by engaging clutch |0| instead of clutch |53, or by engaging both clutches |0| and |53. Any one of these combinations may be utilized if the gears are to be shifted manually, or only a single clutch need be used in place of both clutches 10| and |53 if there is to be manual shifting. However, my automatic shifting mechanism as hereinafter described is simplified by the use of two clutches |0| and |53, which are selectively engaged and disengaged as the different input to output gear ratios are effected through my transmission.

In order to shift into fifth gear clutches 0| and |53 are in the disengaged position and all bands are released, and the only two engaged members are clutches 36 and 38. This causes a two and one-half to one overdrive ratio between shafts 24 and 84.

In the preferred embodiment of my invention, I utilize a hydrokinetic torque converter |2 which may be shifted alternatively between a uid drive connection and a direct drive connection, as heretofore pointed out in column 2, lines 46 to 47. Such a torque converter is shown and described in my application Serial No. 263,419, filed December 26, 1951. The use of such a torque converter permits the operator to use my fivespeed transmission either with the highly efficient direct drive connection or with the highly flexible hydrokinetic torque converter connection. Such a direct drive connection is particularly useful when my transmission is used in connection with relatively light loads.

In order to turn the tractor, tank or other vehicle which utilizes my transmission it is merely necessary to release the reaction member |36 on one side of my transmission by releasing the brake band |38 on that side, so that the reaction member |36 merely idles, and no reaction force is applied to the planet gears |22 on that side of the transmission. Brake band |32 is then moved into operative engagement with brake flange 30 to arrest the rotation of planet carrier |28 and output shaft |28 on that side of the transmission. This will completely stop the track, wheel or other means of locomotion which is attached to output shaft |28 on one side of my transmission, while the track or wheel on the other side of the transmission will continue to receive power through the other output shaft |28 to which it is attached.

Bands |32 are both released, and bands |38 are both engaged for my transmission to be utilized for driving straight ahead instead of for turning.

'Iurning now to my differential unit which is illustrated in Figure 9, this unit may be optionally provided in my transmission. This differential unit is particularly useful in connection with heavy off-the-highway trucks, but it may be used in tractors or tanks or the like.

Gears |40 on reaction drums |36 are connected together through differential shaft which is separated into two portions by means of a clutch |82. Although the clutch |82 illustrated in Figure 9 is a fluid actuated type of clutch similar to the clutches |0| and |53 in Figure l, it is to be understood that clutch |82 can be of any conventional construction.

A gear |84 is integrally mounted on one end of shaft |80 and is in engagement with one of the gears |40. Gear |86 is mounted on the other end of shaft |80 and is in engagement with a reverse gear |88 which also meshes with the other gear |40. Both sections of shaft |80 are journaled in four bearings |90, andshaft |92 which carries reverse gear |88 is journaled in bearings |94.

When clutch |82 is engaged, both portions of shaft |80 are locked together as a unit to form a reaction balancing means between the two gears |40. Normally, when clutch |82 is engaged, the reaction drum bandsV |38 are released, whereby the reaction for each of the drums |36 is provided by the other drum |36 through gears |40, gears |84, gears |86 and |88 and shaft |80. Thus, the load is balanced between the two output shafts |28 of the transmission.

Although clutch |82 is normally disengaged when my transmission is to be used for steering through alternatively releasing the respective bands |38, the advantages of a reaction balancing connection between the two output shafts can be utilized during the steering operation by having clutch |82 engaged, and then alternatively engaging the disengaged bands |32 to steer.

I shall next describe the portion of my automatic shifting mechanism shown in Figures 2 and 3 which determines when a shift will occur, I provide a gear |98 which is mounted on gear 94 in any suitable manner as shown in Figure 1. Gear |96 drives a small differential drive gear |98 which in turn drives a flexible drive cable 200. Disposed intermediate the ends of flexible cable 200 is gear box 202 which has manually operable forward and reverse gears (not shown) therein. Cable 200 is operatively connected to one side of a differential 204.

In a similar manner, I provide a second differential drive gear 200 which is driven by gear |95 as shown in Figures 1 and 2. Gear 206 drives a exible cable 208 having a forward and reverse gear box 2|0 therein. Cable 208 is operatively connected to one side of a diiferential 2|2. A third differential drive gear 2|4 is driven by gear |98 and drives flexible cable ZIE. Cable 2|$ has forward and reverse gear box 2 |8 therein and is connected to one side of a third differential 220.

A flexible drive cable 222 from the engine (not shown) is operatively connected to a pinion gear 224 which is suitably mounted in means not shown. Bevel gears 226, 228 and 230 mesh with pinion gear 224, these bevel gears driving into differentials 204, 2|2 and 228, respectively.

Assuming that gear |98 rotates clockwise during forward transmission operation. This causes gears |98, 208 and 2 |4 to all rotate counterclockwise, and hence the inputs to differentials 204, 2|2 and 228 through cables 200, 208 and 2|8 will all rotate counter-clockwise, assuming that the gear boxes 202, 2|0 and 2|8 are all in the forward drive position. Flexible cable 222 rotates clockwise, whereby the differentials 204, 2|2 and 220 will measure the respective differences in speeds between shafts 200, 208 and 2 I6, and sha-ft 222.

If the transmission is set for reverse operation, then gear boxes 202, 2|0 and 2|8 are all set in reverse drive, whereby the now counter-clockwise rotation of gear |96 will still be transmitted to differentials 284, 2 I2 and 220 as counter-clockwise rotation of cables 200, 208 and 2|8, respectively.

Differentials 204, 2 2 and 228 are provided with output shafts 232, 234 and 236, respectively, these shafts supporting on one end thereof, discshaped, multi-pole permanent magnets 238 which form the input members of eddy-current clutches 248, 242 and 244. The eddy-current clutches are completed by drum portions 245, 248 and 250, which are composed of an electrically conducting 8 material. Drum portions 24B, 248 and 250 are affixed to shafts 252 which are independently journaled in bearings 254 disposed in eddy-current clutch housings 256.

Cams 258 and 280 are provided in the periphery of drum portion 248 of clutch 240, these cams being adapted to selectively actuate the actuating stems 262 and 264 of a pair of fluid valves 288 and 288, respectively. Similarly, cams 210 and 212 on the periphery of drum portion 248 of clutch 242 are adapted to selectively actuate the actuating stems 214, 215 and 218 of fluid valves 280, 282 and 284, respectively. In like fashion, cams 288 and 288 on the periphery of drum portion 250 of clutch 244 are adapted to selectively actuate the actuating stems 290 and 292 of valves 294 and 298. By this arrangement, when the eddy-current clutches are in the positions shown in Figure 4, the transmission will be in low gear. At this time, flexible cables 280, 208 and 2| 8 are all rotating slower than cable 222, whereby the clockwise rotation of cable 222 will predominate over the counter-clockwise rotation of cables 280, 208 and the multi-pole magnets 238 will urge the drum portions of eddycurrent clutches 240, 242 and 244 in a clockwise direction.

Since differential drive gear |88 is the smallest of the three differential drive gears, it will rotate the fastest of the three, and when its speed becomes greater than that of cable 222, the output o'f differential 204 will rotate counter-clockwise, whereby drum portion 246 of eddy-current clutch 240 will move counter-clockwise, actuating valves 288 and 268 to shift the transmission from low to second gear.

Similarly, when differential drive gear 280 rotates faster than cable 222, the output of differential 2|2 will rotate counter-clockwise, whereby drum portion 248 of eddy-current clutch 242 will move counter-clockwise, actuating valves 280, 282 and 284. In like fashion, valves 294 and 285 are actuated by rotation of gear 2|4 and cable ZIE faster than cable 222.

In order to more clearly describe my automatic shifting mechanism, reference will now be made to the curves shown in Figure 8. Curve A is a plot of torque converter efficiency against output to input speed of the converter. Curve B is a plot of the torque multiplication ratio against output to input speed of the converter. Curve C is a plot of engine torque against engine speed, which reaches a maximum of approximately 1800 R. P. M.

Curves A and B illustrate that with the proper gear ratios in my transmission, and upon proper timing of my automatic shifting, my converter may be continuously operated at its peak efficiency, above put speed ratio is 30%, the efficiency, as shown by curve A, is 80%, and the torque multiplication by the converter, as shown in curve B, is 3 to 1. As the output to input speed ratio climbs` from 30% the efciency shown by curve A remains above 80% until the output to input speed ratio becomes 60%, at which time the efficiency is 80% again, and the torque multiplication, as shown by curve B, is 11/2 to 1. Thus, in the peak efficiency of the converter, there is a 2 to l speed and torque change. By selecting the gear ratios in my automatic changespeed transmission as multiples of this 2 to l change, I am able to keep the converter operating above 80% eiciency.

Thus, my low gear, as heretofore indicated,

When the output to in is a 4 to l reduction, and when it is operatively engaged as a starting gear, curves A and B are followed from an output to input speed ratio of to a ratio of 60%, at which time there will be an automatic shift from the 4 to 1 reduction of low gear to the 2 to l reduction of second gear. This automatic shift to second gear will instantaneously change the converter output to input shaft speed ratio from 60% to 30%, and the curves A and B will be followed in second gear from 30% to 60% output to input ratio, at which time there will be another automatic shift, this time from second gear to third gear, which has a 1 to l gear ratio. Again, this shift to third gear will move operation of the converter back to the 30% output to input ratio, and the curves A and IB will be followed back up to 60% at which time the third and last automatic shift will occur. Shifting from third to fourth gear and again moving operation back to the 30% output to input ratio in the converter.

Similarly, when my transmission is in fourth gear, and the ratio of output to input shaft Speeds of the converter is reduced to 30%, there will be an automatic shift back down to third gear and the output to input shaft speed ratio will become 60% again. When the output to input ratio becomes 30% in third gear, there will be an automatic shift down to second gear. The shift back down to low gear from second will occur in the same manner when the output to input speed ratio reaches 30% in second gear.

In order to effect the automatic shifts at the proper times so that the curves of Figure 8 may be followed as heretofore described, it now only remains necessary to provide the proper speed ratios in the drives to the differentials 2M, 2l2 and 220. In the ideal case, assuming that the eddy-current clutch 2M would operate at exactly the point of reversal of the direction of rotation of differential output shaft 232 to shift the transmission from low gear to second gear, the gear ratio between gears |96 and 93 would be such that when the Converter is at the 60% output to input shaft speed ratio, the cables 200 and 222 would rotate at exactly the same speed. Similarly, in shifting down from second to low gear, in the ideal case, the cables 200 and 222 would be rotating at the same speed when the converter output and input shafts have a 30% speed ratio.

This same situation would be true in the ideal case where there is a shift from second to third gear, the gear ratio between gears 206 and E96 being such that at 60% output to input speed of the converter, cables 208 and 222 are rotating at the same speed. Such is also the case regarding a shift from third to fourth gears, considering the gear ratio between gears 211i and ist and the speeds of cables 2l6 and 222.

However, in the ideal case as outlined above for a shift up, if the transmission output shafts do not continue to increase in speed, but remain at the same speed at which the shift occurred, or are slowed down slightly after the shift, there will be an immediate shift back down. Such shifting back down is avoided in the following manner:

In actual operation when shifting through the gears, the output shafts of the differentials must turn anti-clockwise at from 15 to 20 R. P. M. in order to provide a sufficient force to actuate the fluid valves. rIlhus, if the gear ratios of gears l98, 206 and 2M to gear |96 are those indicated in the above ideal case, then the shifts upward would not occur until the output to input speed ratio of the converter shafts is somewhat greater than This will cause a change in the converter output to input shaft ratio to somewhat greater than 30% due to the 2 to l change in any shift for my transmission. This will be in a stable zone of operation, because to shift back down, it will require a speed of the output shaft of the shifting differential of from l5 to 20 R. P. M. clockwise, so that this shift will only occur at a converter output to input speed ratio somewhat below 30 R. P. M. Thus, any unnecessary shifting back and forth at the shifting points is completely eliminated.

t should be noted that a much larger increment in the speed of gear L96 is necessary to produce the required l5 to 20 R. P. M. output speed of the differential 220 than is required to produce the same differential output speed in differential 2|2, for the reason that gear 2id is larger than gear 2%, while these two gears both mesh with gear ist. Similarly, it takes a larger increment in the speed of gear llli to produce the required 15 to 20 R. P. M. output speed of differential 220 or 2i2 than is required to produce the same differential output speed in differential 2M. For this reason, the least stable shift will be that from low to second gear, as the l5 to 20 R. P. M. clockwise of the output shaft of differential 2M necessary to shift back down to low from second gear will be caused by a much slighter lowering of the speed of gear ESG than would be required to shift back down from fourth to third or from third to second. The most stable shift iwill be from third gear to fourth gear. In like manner, the most stable shift down will be from fourth gear to third, and the least stable will be from second to low.

Compensation can be made for this difference in the stability of the shifts between the various gears in one of several different ways. One method of compensation is to build the valves 266 and 268 in such a manner that more force is required to move the valve actuating stems 252 and 261i than is required to move the actuating stems Z'Hl, 215 and 218 of valves 281i, 282 and 285i. Similarly, less force would be required to shift the stems 290 and 292 than any of the other actuating stems. By this means, the dif ference in speed between cables 200 and 222 to cause a shift would be greater than the difference in speed of cables 20B and 222, or 2id and 222, whereby the same increment in the speed of shaft 96 from the speed where the converter output to input speed is at the ideal shifting point will be required to make any one of the three automatic shifts either up or down.

Another method of compensation, which is my preferred method, is to so arrange the gear ratios between the respective gears igt, and :2l-i, and gear lil that the shifts will occur at points on curve A in Figure 8 other than the 30% and 60% output to input speed ratios of the converter. rlhe basis for this means of compensation is that when there is a shift from a point of lower efliciency on the converter efficiency curve to a point of higher efficiency, there will be an instantaneous increase in the speed of the converter output shaft, and hence an instan taneous increase in gear It. rThus, if a shift upward is being made, and that shift point is for a converter output to input shaft speed ratio of greaterthan 60%, the shift back will be to a converter output to input shaft speed ratio of greater than 30%, which is at a higher converter eiciency than when the speed ratio is greater than 60%, whereby there will be an instantaneous increase in the speed of the gear 196 and the shift will be a stable one. Similarly, these same shift points may lbe used for a downward shift, for the reason that to have a stable downward shift, it is desirable to have an instantaneous decrease in the speed of gear |96. Such a. decrease will be caused by a shift from a point of greater than 30% converter output to input speed to a point of greater than 60% converter output to input speed.

In using such a spacing to the right from the 30%-60% region of curve A of Figure 8, the amount of the spacing will determine the increase or decrease in the emciency for any single shift, thereby determining the amount of added stability which is given to the shift. Since the shift from low to second, and back to low was the least stable shift, it is desirable to cause a greater instantaneous increase in the speed of gear 196 for this shift than for the others. A jump in the eiiiciency of any given amount upon a shift will cause a given increase in the speed of gear 196, whereby the smaller gear 198 will cause a greater jump in the speed of cable 200 than will be caused in the speed of cable 206 from gear 206. Thus, for a given spacing to the right on curve A in Figure 8, there will be a greater stability given to the shift from low to second and back than will be given to the other shifts. This compensates for the lesser stability in the shift out of and into low gear which was heretofore indicated. Points 291 and 299 on curve A in Figure 8 indicate shift points above the 60% and 30%, respectively, values for the output to input shaft speed ratios for the converter.

Having described my five-speed transmission, the differential unit which may bc applied thereto and the differential means for determining when the automatic shifts shall occur, I shall now describe the valves which actually shift my transmission and their operation.

Looking to Figure 7 which is a sectional view of valve 266, I provide a cylindrical valve body 298 having a cap 300 which screws into the top thereof. The bottom of valve body 293 is flanged inwardly to provide a passage to receive actuating stem 262, and is provided with a sealing ring 302 which prevents uid from escaping valve 266 between valve body 298 and actuating stem 262. Actuating stem 262 is integrally attached to the bottom of a valve element 1304 which is urged downward within valve body 298 by means of a spring 306 compressed between cap 300 and the top of valve element 304. A passage 30'1 connects the upper and lower faces of valve element 364 to prevent pressure from building up in the ends of valve body 266 when valve element 304 is moved up and down.

When valve element 304 is in its lowermost position, which is the normal position, an annular recess 308 in valve element 304 connects fluid line 310 to exhaust line 312 which leads to a fluid reservoir (not shown). Line 310 communicates with a line 314. In this normal position of valve element 304 uid is not permitted to pass from a fluid pressure line 1316 into line 314, as communication between these lines is blocked off Iby valve element 304. However, when actuating stem 262 is cammed upward, valve element 304 moves upward to permit fluid to flow from iiuid pressure line 316 into line 314. At the same time, upward movement of valve element 304 moves annular recess 308 out of communication with lines 316 and 312, whereby the exhaust is blocked off. The other valves 268, 260. 262, 294 and 296 are similarly constructed.

When the engine (not shown), which is operatively connected to my transmission, is rst started up and the transmission is in low gear, the drum portions 246, 248 and 250 of eddycurrent clutches 240, 242 and 244 are in the positions shown in Figure 4. Rotation of the drum portions 246, 248 and 250 clockwise is restricted by engagement between lugs 316 on the drum portions and lugs 320 on valves 266, 280 and 294, and rotation of the drum portions anti-clockwise is similarly limited by engagement between lugs 322 on the drum portions and lugs 324 on valves 266, 260 and 294. Thus, when the transmission is started up in low gear, drum portions 246, 246 and 256 are all in the position shown in Figure 4 with lugs 316 and 320 in engagement.

In the low gear position, valve 266 is set to admit fluid pressure into line 314 from pressure line 316, and to block oil exhaust line 312. Fluid pressure in line 314 actuates brake band 18 by any conventional means (not shown). Fluid pressure is also admitted through valve 280 to line 326 from pressure line 328, the exhaust portion of valve 280 being closed off. This actuates clutch 36 by any conventional means. In the low gear position, valve 268 is exhausted.

When the point is reached to shift from low to second, drum portion 246 is rotated anticlockwise, being stopped by engagement between lugs 324 and 322 in the position shown in Figure 5. This causes valve 266 to exhaust, and valve 266 to admit iluid pressure from pressure line 330 to line 332 which connects valves 26B and 262. Movement of valve 266 to the exhaust position releases band i6, and movement of valve 266 to the position to admit fluid pressure to line 332 causes uid pressure to pass through valve 282, which is in the actuated or pressure admitting position, into fluid line 334 which admits fluid to the fluid operable clutch 101 to cause engagement thereof.

In order to cause the shift into third gear, drum portion 248 of eddy-current clutch 242 moves anti-clockwise until lugs 322 and 324 come into contact. This moves both valves 280 and 282 into the exhaust position, thereby permitting the fluid to be exhausted from fluid lines 326 and 334, respectively, through the respective exhaust lines 336 and 338. This releases clutches 36 and 101. At the same time, valve 284 is moved into the position to admit pressure from iiuid pressure line 340 into fluid line 342. Line 342 is then in communication with line 344 through valve 296 which is in the pressure position. A line 346 connects with line 342 before the latter line reaches valve 206. Fluid pressure through line 344 causes engagement of band 66 by any conventional means, and ucl pressure through line 346 engages clutch 38 by any conventional means to complete the shift into third gear.

The automaticl shift into fourth gear is effected by rotation of drum portion 250 of eddy-current clutch 244 anti-clockwise to the point where lugs 322 and 324 contact. This causes valve 296 to exhaust fluid from line 344 out through line 348 and valve 294 to admit iluid pressure from uid pressure line 350 to uid line 352. Exhausting fluid from line 344 releases band 60, and the admission of duid pressure to line 352 causes en- 13 gagement of fluid operable clutch 53 to complete the engagement of fourth gear.

Although I have provided automatic shifting between only four out of the five of my transmission ratios in order to preserve simplicity of construction and desirable operation features, it is to be understood that by the provision of another shifting differential and another eddy-current clutch and associated valve mechanism the automatic shifting could be carried through all nve gears. It is also to be noted that my automatic shifting will operate in the same manner in both forward and reverse gears, the only manual control within the nrst four transmission ratios being the shift between forward and reverse.

The automatic shifting back down through the gears from fourth gear down into low gear is effected in exactly the reverse manner from the shifting upward through the gears. Thus, the automatic shift from fourth gear to third gear is caused by rotation of drum portion 255 back clockwise until lugs 3i8 and 32a engage. This causes exhausting of line 352 through valve 291i to release of clutch 153, the exhausted fluid being conveyed to the reservoir (not shown) by means of exhaust line 35d. Valve 29s is opened to admit pressure to line 3M to actuate band 60.

In a similar manner the shift back from third gear to second gear is effected by rotation of drum portion 2&8 of eddy-current clutch 242 clockwise, and the shift back down into low gear is caused by rotation of drum portion 245 clockwise.

Although the preferred form of my invention includes the automatic shifting mechanism, it is to be understood that my five-speed transmission comprising a single, compact unit is an advance in the art even without the automatic shifting mechanism. Thus, my invention also contemplates the use of my five-speed transmission in connection with manual controls for actuating the same elements that were actuated by the automatic controls.

One of the advantages of the particular construction of my automatic shifting mechanism is that it consists solely of mechanical and duid connections, and electrical circuits form no part of it. For this reason, my automatic shifting mechanism is particularly durable and positive in performance, even under the most adverse operating conditions. In this connection it should be noted that none of the moving parts are left exposed. Thus, the transmission gears are enclosed within the transmission housing I iii,

which also contains the differential drive gears |98, 206 and 2id, differentials 254, 262 and 22d are contained in a housing (not shown) and the eddy-current clutches are encased within nous ings 256. The only moving members of the valves on the outside thereof are the valve actuating stems, but the valves are so positioned, as shown in Figure 6, that these stems are completely sealed within the eddy-current clutch housings. The differential unit shown in Figure 9 is merely a part of the transmission within housing |44.

Another great advantage of my automatic shifting mechanism is that it will always shift my transmission in such a way that the torque converter between the engine and the transmission continuously operates above a predetermined high efficiency. This is an important factor in rendering my invention commercially acceptable, for not only does it greatly decrease the fuel consumption of the engine and thus decrease the operating expense, but it also insures that at least a given percent of the power output of the engine will be delivered to the driven elements.

In operating my automatic transmission for driving straight ahead it is only necessary to adjust the throttle according to operational demands, and the transmission will smoothly supply the desired torque and output speed. Since the automatic shifts cause a jump between substantially 30% and 60% converter output to input speed, curve A in Figure 8 shows that at most, there will be only a small change in the eficiency of the converter at the time when a shift is made, whereby there will be only a small instantaneous change in the transmission output speed and little or no jerking will be felt in the driven elements.

If the operator then desires to diiferentially connect the two transmission output shafts, it is only necessary that he move a single valve which will actuate the differential clutch 32 to engage the differential.

If the tractor, tank or other tracked vehicle in which my invention is installed is to be steered by use of the transmission itself, it is only necessary to actuate a steeringwheel, or one or two levers, to selectively release the brake band |38 and engage the band i312 on either side of the transmission.

The shifting mechanism in the present application is an improvement of my application Serial No. 254,506', filed November 2, 1951, for Power Transmitting Apparatus, which is a division of my application Serial No. 647,677, filed February 15, 1946, for Transmission for Well Drilling Machinery. The transmission portion of the present invention is a novel arrangement of various elements shown in my application Serial No. 90,473, liled April 29, 1949, now abandoned, for Change-Speed Transmission, and of my application, Serial No. 254,506, led November 2, 1951, for Power Transmitting Apparatus.

It is to be understood that the form of my invention herein shown and described is my preferred embodiment and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of my invention, or the scope of the appended claims.

I claim:

1. A power transmission including a planetary gear system having a pair of axially aligned tubular planetary input shafts and a single planetary output shaft centrally positioned within said tubular shafts, a clutch operatively engageable between said output shaft and one of said tubular shafts to alternatively lock the shafts together or permit independent rotation of the shafts, a gear on each end of said output shaft, said gears being in driving relationship, respectively, with planetary reduction gears having planet cages and reaction drums, and braking means on said planet cages and on said drums to alternatively permit rotation of the said cage and locking of the said drum or rotation of the said drum and locking of the said cage on one or both ends of ent rotation of the shafts, a gear on each end of said output shaft, said gears being in driving relationship, respectively, with planetary reduction gears having planet cages and reaction drums, and braking means on said planet cages and on said drums to alternatively permit rotation of the said cage and locking of the said drum or rotation of the said drum and locking of the said cage on one or both ends of said transmission.

3. A power transmission including a planetary gear system having a pair of axially aligned tubular planetary input shafts and a single planetary output shaft centrally positioned within said tubular shafts, a clutch operatively engageable between said output shaft and one of said tubular shafts to alternatively lock the shafts together or permit independent rotation of the shafts, a gear on each end of said output shaft, said gears being in driving relationship, respectively, with planetary reduction gears having planet cages and reaction drums, braking means on said planet cages and on said drums to alternatively permit rotation of the said cage and locking of the said drum or rotation of the said drum and locking of the said cage on one or both ends of said transmission, and means for driving said tubular input shafts at different speed ratios from a Common power source.

4. In a vehicle, a transmission for supplying power and for steering which includes a planetary gear system having a pair of axially aligned tubular planetary input shafts and a single planetary output shaft centrally positioned within said tubular shafts, a clutch operatively engageable between said output shaft and one of said tubular shafts to alternatively lock the shafts together or permit independent rotation of the shafts, a gear on each end of said output shaft, said gears being in driving relationship, respectively, with planetary reduction gears having planet cages and reaction drums, respectively, a brake on each of said planet cages and a brake on each of said reaction drums, said planet cage brakes being normally disengaged and said reaction drum brakes being normally engaged for straight propulsion of said vehicle, and means for simultaneously engaging one of said planet cage brakes and disengaging the corresponding reaction drum brake to steer said vehicle.

5. A power transmission including a planetary gear system having a pair of axially aligned tubular planetary input shafts and a single planetary output shaft centrally positioned within said tubular shafts, said tubular input shafts having a two to one gear ratio through said planetary gear system, a clutch operatively engageable between said output shaft and one of said tubular shafts to alternatively lock the shafts together or permit independent rotation of the shafts, a gear on each end of said output shaft, said gears being in driving relationship, respectively, with planetary reduction gears having planet cages and reaction drums, braking means on said planet cages and on said drum to alternatively permit rotation of the said cage and locking of the said drum or rotation of the said drum and locking of the said cage on one or both ends of said transmission, and selective means for driving said tubular input shafts at speed ratios differing by a multiple of two from a common power source.

6. An automatic shifting mechanism including a multiple speed transmission having input and output shafts, an engine operatively connected to said input shaft, a device for measuring the relative speeds of said engine and said transmission output shaft, an operative connection between said engine and said measuring device, a plurality of geared operative connections having progressively stepped ratios between said output shaft and said measuring device, an automatic shifting unit for automatically shifting said transmission, and an operative connection between said measuring device and said automatic shifting unit.

7. An automatic shifting mechanism including a multiple speed transmission having input and output shafts, an engine operatively connected to said input shaft, a plurality of differentials, each having a pair of input members and an output member, an operative connection between said engine and one input member of each of said differentials, a plurality of geared operative connections having progressively stepped ratios between said output shaft and the other input members of the respective said differentials, an automatic shifting unit for automatically shifting said transmission, and an operative connection between the output member of each of said differentials and said automatic shifting unit.

8. An automatic shifting mechanism including a multiple speed transmission having input and output shafts, an engine operatively connected to said input shaft, a plurality of differentials, each having a pair of input members and an output member, an operative connection between said engine and one input member of each of said differentials, a plurality of geared operative connections having progressively stepped ratios between said output shaft and the other input members of the respective said differentials, an automatic shifting unit for automatically shifting said transmission, the input members of said automatic shifting unit ccmprising a plurality of eddy-current clutches, and operative connections between the output inembers of said differentials and the respective said eddy-current clutches.

9. An automatic shifting mechanism including a multiple speed transmission having input and output shafts, an engine operatively connected to said input shaft, a plurality of differentials, each having a pair of input members and an output member, an operative connection between said engine and one input member of each of said differentials, a plurality of geared operative connections having progressively stepped ratios between said output shaft and the other input members of the respective said differentials, a plurality of eddy-current clutches having input and output members, operative connections between said eddy-current clutc input members and said differential output members, respectively, a fluid valve having inlet and outlet ports operatively connected to each of said eddy-current clutch output members, a source of fluid pressure connected to each of said fluid valve inlet ports and an operative connection between each of said fluid valve outlet ports and said transmission to effect shifting of said transmission upon actuation of said valves.

i0. In a vehicle, a transmission for supplying power and for steering which includes a planetary gear system having a pair of axially aligned tubular planetary input shafts and a single planetary output shaft centrally positioned within said tubular shafts, a clutch operatively engageable between said output shaft and one of said tubular shafts to alternatively lock the shafts together or permit independent rotation of the shafts, a gear on each end of said output shaft, said gears being in driving relationship, respectively, with planetary reduction gears having planet cages and reaction drums, respectively, a brake on each of said planet cages and a brake on each of said reaction drums, said planet cage brakes being normally disengaged and said reaction drum brakes being normally engaged for straight propulsion of said vehicle, and means for simultaneously engaging'one of said planet cage brakes and disengaging the corresponding reaction drum brake to steer said vehicle.

11. A power transmission device including a multiple speed transmission having input and output shafts, an engine operatively connected to said input shaft, a device for measuring the relative speeds of said engine and said transmission output shaft, an operative connection between said engine and said measuring device and a plurality of geared operative connections having progressively stepped ratios between said output shaft and said measuring device.

12. A power transmission device including a multiple speed transmission having input and output shafts, an engine operatively connected to said input shaft, a plurality of diiferentials, each having a pair of input members and an output member, an operative connection between 18 said engine and one input member of each of said diiferentials and a plurality of geared operative connections having progressively stepped ratios between said output shaft and the other input members of the respective said differentials.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,872,541 White Aug. 16, 1932 1,964,956 Lincoln July 3, 1934 2,164,729 Wilson July 4, 1939 2,171,715 Sinclair Sept. 5, 1939 2,272,934 Cotal Feb. 10, 1942 2,302,714 Pollard Nov. 24, 1942 2,314,664 Shenstone Mar. 23, 1943 2,484,011 Brunken Oct. 11, 1949 2,523,766 Kelley Sept. 26, 1950 2,529,129 Blair Nov. 7, 1950 2,560,554 -Colby July 17, 1951 2,569,651 Bonnan Oct. 2, 1951 2,585,790 Kelley Feb. 12, 1952 2,589,119 OLeary Mar. 11, 1952 2,594,064 OLeary Apr. 22, 1952 FOREIGN PATENTS Number Country Date 461,947 Great Britain Feb. 26, 1937 

